[time-nuts] Lucent RFTG-m-XO

Robert E. Martinson REMartinson at rcn.com
Fri Feb 2 11:29:58 EST 2007

Thanks for the quick replay.

Yes the 10 MHz directly at the oscillator output is about 60 mHz high (I
adjusted it several days ago, it was close even before), plenty close enough
I would think.  Unit only needs 410 mA when warmed up, power supply is 3 amp
so no prob.

Sure wish I knew what the  fault was, I suspect if I had a way of
monitoring/controlling the unit via the RS-485 buss the info might be
available.  It seems the XO unit does not spew data out the 485 port, it
waits for an interrogation?????  I see no activity with a scope.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jason Rabel
Sent: Friday, February 02, 2007 11:08 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Lucent RFTG-m-XO

I do not recall if you mentioned this before or not, but did you probe the
OCXO itself to make sure it was sending out 10 MHz (or close to that)? Is
your 24V power supply able to supply enough amps?

The Motorola's expect an antenna to draw power within a certain range. It's
possible that they simply shunted that current to keep the false-alarms to a
minimum and used power from the secondary board and allow a wider range of
current draw, maybe not even monitoring the current.


> I'm trying a 24 hour run now with the XO unit just in case I never let it
> run long enough previously.  Also it's all buttoned-up just in case some
> external RF source was disturbing it previously.  The only connections are
> 24 VDC & the antenna.
> The Fault & No GPS lamps are on & there is NO 15 MHz present on the front
> panel SMA connector.  With a scope I see no activity on J5.
> Interestingly, the 5 VDC for the antenna comes from the daughter board,
> the GPS receiver.  This verified by measuring 5 VDC on the TNC connector
> with the GPS receiver unplugged.  I guess this allows them to sense an
> antenna fault.  I tried various dummy loads (resistors) to simulate from
> about 10-80 ma antenna loads.  The fault lamp never extinguished.
> Maybe I really have a faulty XO unit??
> Are the RS-485 connections on J5 2-wire or 4-wire??  Has anybody managed
> make any sense of the data &/or commands??
> REMartinson, N1VQR

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